256       Dr.  C.  R.  A.  Wright  on  the  Relations  between  the 
it  is  frequently  noticed  that  the  formula  is  dissected  in  different 
ways  in  accordance  with  different  reactions.  Usually  all  these 
ways  may  be  expressed  in  one  single  formula  by  carrying  the  dis- 
section so  far  as  to  break  up  the  formula  into  several  groups,  of 
which  fewer  or  more  are  taken  together  to  form  the  particular 
radical  required  in  any  given  reaction.  Thus  the  action  of  acetyl 
chloride  on  water  gives  rise  to  the  dissected  formula  C2  H3O.OH 
for  acetic  acid  ;  the  production  of  this  acid  from  methyl  cyanide 
gives  rise  to  the  differently  dissected  formula  CH3  .  CO2  H  ;  both 
of  these  reactions,  however,  can  be  expressed  by  carrying  the 
dissection  to  this  point  CH3 .  CO  .  OH.  It  is  usually  found  that 
formulae  thus  dissected  into  very  simple  groups  are  capable  of 
expressing  all  the  reactions  of  the  body  in  question;  thus  the 
formula  CH3 .  CO  .  OH  expresses  not  only  the  above  two  re- 
actions, but  also  the  following, 
C2H5.OH  +  02  =  H20  +  C2H3O.OH, 
CH3 .  CO  .  OH  =C02  +  CH3 .  H, 
CH3— CO— OH  +  CH3— CO— OH  =  CO  (OH)2  +  CH3— CO— CH3, 
CH3— CO— OH  +  H— CO -OH     =CO  (OH)2  +  H— CO— CH3, 
&c. ;  i.  e,  all  reactions  lead  (usually)  to  the  same  final  dissection. 
25.  In  a  few  instances,  however,  it  is  found  that  different  re- 
actions lead  to  different  final  dissections.  Thus  the  reactions  of 
ethylene  dibromide  and  of  glycol  lead  to  the  dissected  formula 
for  the  latter  OH— CH2— CH2— OH  ;  the  reactions  of  aldehyde 
lead  to  the  formula  CH3 — CO — H.  When  glycol  is  dehydrated 
by  zinc  chloride,  aldehyde  is  produced ;  and  this  would  lead  to 
the  formula  for  glycol,  CH3— CH  (OH)2. 
Similarly  the  reactions, 
Glycol  iodhydrin  and  zinc  methyl  =  zinc  iodomethide  and 
isopropyl  alcohol, 
Ethylidene  dichloride  and  potassium  cyanide,  product  with 
caustic  potash  gives  ordinary  succinic  acid, 
Trimethyl  carbinol  and  oxygen  give  water  and  isobutyric 
acid, 
indicate  the  dissected  formulae  of  the  first-named  generators  to 
be  respectively 
CH3— CHI— OH:  CI— CH—  2CH2— CI :  OH— CH2— CH(CH3)2, 
instead  of 
I— CH2— CH2— OH,     CH3— CH  CI2,     OH— C(CH3)3, 
ese  latter  formula?  being  those  derived  from  the  majority  of 
e  reactions  of  these  bodies. 
Cases  of  this  kind  are,  comparatively  speaking,  so  rare  as  not 
